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Founded in 1904 and headquartered in Farmington Hills, Michigan, USA, the American Concrete Institute is a leading authority and resource worldwide for the development, dissemination, and adoption of its consensus-based standards, technical resources, educational programs, and proven expertise for individuals and organizations involved in concrete design, construction, and materials, who share a commitment to pursuing the best use of concrete.
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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Title: Air Voids in Concrete: A Study of the Influence of Superplasticizers by Means of Scanning Electron Microscopy and Optical Microscopy
Author(s): R. Pleau, M. Pigion, R. M. Faure, and T. Sedran
Publication: Special Publication
Appears on pages(s): 105-124
Keywords: air-entrained concretes; air-entraining agents; air entrainment; capillarity; electron microscopes; freeze-thaw durability; microscopy; plasticizers; porosity; voids; Materials Research
Abstract:Samples from nine air-entrained concrete mixes made with and without a superplasticizer were examined under a scanning electron microscope to determine the size distribution of the voids in the 0.5 to 50 æm range. Concurrently, samples of the same mixes were examined under a binocular microscope to determine the size distribution of the voids in the 10 to 1000 æm range. The voids observed under the electron microscope were separated into two categories: air voids (spherical in shape or nearly so) and large capillary pores (irregularly shaped). The results show that, in mixes, the amount of capillary pores with diameters ranging from 0.5 to 50 æm is relatively important (the number of these voids generally represents approximately half the total number of entrained air voids). The role of these pores in the frost resistance of concrete is believed to be strongly dependent on their degree of saturation at the time of freezing. The number of air voids smaller than 10 æm in diameter, however, was found to represent less than 10 percent of the total number of entrained air voids. These small air voids are thus expected to have little influence on frost durability. The results also indicate that the distribution of the ir-void diameters is influenced by the nature of the air-entraining agent but not by the use of a superplasticizer. The distribution of air-void diameters was found to be approximately the same for all mixes, irrespective of the value of the spacing factor.
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